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 Post subject: DDS transmitter
PostPosted: Jul Tue 28, 2020 12:53 pm 
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Posts: 974
Location: Katy, Texas
Has anyone here built a DDS transmitter for AM low power broadcasts?


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 Post subject: Re: DDS transmitter
PostPosted: Jul Tue 28, 2020 11:20 pm 
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Location: Saskatoon
This isn't a complete transmitter, but a number of forum members have used this as the exciter for some of the various transmitter projects that have been posted on the forum.
viewtopic.php?f=12&t=82833&start=0

Also, I've used an AD9851 as the frequency source for a one tube transmitter.


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 Post subject: Re: DDS transmitter
PostPosted: Jul Tue 28, 2020 11:58 pm 
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Location: Lexington, KY USA
https://www.antiqueradios.com/forums/viewtopic.php?f=12&t=82833&start=0
$12 MW Frequency Generator for Part 15 transmitters
Not exactly what you asked for, but may be what you need.

This is good for driving an AM modulator stage.

Ted

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 Post subject: Re: DDS transmitter
PostPosted: Jul Wed 29, 2020 12:30 am 
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Location: Katy, Texas
Thank folks. I was think more inline with these things you can buy on ebay but homebrew instead..

https://www.ebay.com/itm/AM-MW-RADIO-BA ... Sw5EdbHBmA

Steve


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 Post subject: Re: DDS transmitter
PostPosted: Jul Wed 29, 2020 11:22 am 
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$160 sure is a LOT of money for what it is, but, if you're incapable of, or just don't want, to alter a far less expensive DDS, what you suggest, is an option.

There are DDS units for 25 bucks out there, which can be easily modified for A.M. operation.

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 Post subject: Re: DDS transmitter
PostPosted: Jul Wed 29, 2020 10:49 pm 
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Location: Katy, Texas
thats what I was looking for .. the plans from others that may have already done it.


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 Post subject: Re: DDS transmitter
PostPosted: Jul Thu 30, 2020 9:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Saskatoon
You need to be aware that even if you have some sort of digitally tuned transmitter, you can't simply punch in a frequency and expect it to put out a signal having any significant range, without also tuning the antenna. I haven't yet seen any hobby grade DDS transmitter that can do that. So, the antenna tuning is still going to be a manual adjustment.

It would make for a very interesting project to develop an automatic antenna tuner for a Part 15 transmitter.


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 Post subject: Re: DDS transmitter
PostPosted: Jul Thu 30, 2020 10:46 pm 
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high bob. Ya that exactly the kind of stuff that i was hoping someone had already done. Modulating, amplifying, matching, etc.


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 Post subject: Re: DDS transmitter
PostPosted: Jul Thu 30, 2020 11:15 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Saskatoon
Frequency generation, modulation and amplifying has already been done many times and in many different ways. You can mix and match the sections as you like.

Antenna matching still remains a manual adjustment as far as I'm aware, but an automatic matcher should be doable. These units exist for amateur radio equipment.


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